The present invention relates to an industrially advantageous process for preparing a trans-.beta.-aroylacrylic ester having the formula (III): ##STR1## wherein R.sup.1 is an alkyl group having 1 to 4 carbon atoms and A is an aryl group which may be substituted by at least one substituent selected from the group consisting of a halogen atom, hydroxyl group, nitro group, cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms and trifluoromethyl group, which is important as an intermediate material for preparing a medicament, a perfume or the like.
Hitherto, various processes have been known as processes for synthesizing an aroylacrylic ester. For example, in case of a benzoylacrylic ester, following processes have been known.
(1) A process esterifying a benzoylacrylic acid (See Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences, Serie BCD, 232, 2326 (1951) [CA, Vol 46, 943], Japanese Unexamined Patent Publication No. 103042/1987 and Japanese Unexamined Patent Publication No. 130564/1988.)
(2) A process eliminating a substituent from a benzoylpropionic ester having a substituent at the .alpha.- or .beta.-position.
i) A process dehydrohalogenating a benzolylpropionic ester having a halogen atom at the .alpha.-position (See Journal of American Chemical Society, 45, 233 (1923) and Bulletin de la Societe Chimique de France, 1075 (1950).) PA1 ii) A process eliminating an alcohol from a benzoylpropionic ester having an alkoxyl group at the .alpha.-position (See Japanese Unexamined Patent Publication No. 103042/1987.) PA1 iii) A process eliminating pyrrolidine from a benzoylpropionic ester having pyrrolidinyl group at the .alpha.-position (See Tetrahedron Letters, 29, 3997 (1988).) PA1 iv) A process eliminating methylsulfenic acid from a benzoylpropionic ester having methylsulfinyl group at the .beta.-position (See Journal of American Chemical Society, 98, 3305 (1976).) PA1 v) A process eliminating phenylsulfenic acid from a benzoylpropionic ester having phenylsulfinyl group at the .alpha.-position (See Tetrahedron Letters, 24, 323 (1983).) PA1 Column: COSMOSIL 5C.sub.18 -AR made by Nacalai tesque 4.6 mm i.d..times.250 mm PA1 Mobile phase: 50% acetonitrile in 0.1M phosphate buffer (pH 2.5) PA1 Flow rate: 1.0 ml/min. PA1 Column temperature: 30.degree. C. PA1 Detection: UV 210 nm
(3) A process according to Wittig reaction with an arylglyoxal and an alkyl glyoxylate (See Collection of Czechoslovak Chemical Communications, 37, 3950 (1972) [CA, 78, 83984].)
However, in case of the process (1) esterifying a benzoylacrylic acid, the material, a benzoylacrylic acid itself should be synthesized according to a process such as Friedel-Crafts reaction of a benzene with maleic anhydride/aluminium chloride (see Journal of American Chemical Society, 70, 3356 (1948)) or aldol condensation of an acetofenone with glyoxylic acid/acetic acid (see Japanese Examined Patent Publication No. 39020/1977), wherein complicated operations are required for treatment of effluent, and it is complicated to control the formation of byproducts during esterification. Therefore, the process (1) is not necessarily recognized to be an advantageous process.
In both cases of the process (2) eliminating a substituent and the process (3) according to Wittig reaction, expensive materials are used, reaction processes are long and yields are low. Therefore, the processes (2) and (3) are not recognized to be practically useful in the industry.
An object of the invention is to provide a novel process for preparing a trans-.beta.-aroylacrylic ester which is excellent in operability, safety, economy and the like and is therefore practically useful in the industry, solving the above mentioned problems.